Conventional Motion Picture Expert Group (MPEG) video display systems implement three areas of memory to store picture data (or images) for decoding and displaying called frame stores. However, in some cases the three frame store video display implementations do not provide sufficient time to perform additional graphics manipulation after the picture data has been decoded. Additional time is needed to perform post-decode graphic manipulation in conventional video display systems.
To perform post-decode graphic manipulation, conventional video display systems (i) implement faster graphics mixing systems, (ii) only apply graphics mixing in certain cases where sufficient time is guaranteed, and/or (iii) reduce and/or limit the amount of graphics mixing performed. Conventional video display systems (i) are implemented with a much faster (and hence more expensive) graphics post-processing system, and/or (ii) limit the features that can be added to the system.
Furthermore, arbitrary vertical scaling is desired by a number of users. Arbitrary vertical scaling can provide (i) a feature for differentiation among set-top box (STB) vendors and (ii) a better user experience. However, vertical scaling is constrained in three frame video display methods and/or architectures since three frame video displays decode and display simultaneously out of the same frame store under certain conditions without decode overwriting display (i.e., the picture will not have been fully decoded before it is displayed). Simultaneous decode and display out of the same frame store forces the decode to run more slowly and results in video tears as downscaling increases.
A conventional Motion Picture Expert Group (MPEG) decode system is implemented having three frame stores. Two frame stores are configured to store the forward and backward anchor frames (e.g., reference pictures) and the third store is configured to store the B frame. The B frame store is configured to receive information copied from the forward and backward anchor frames. Conventional video decoders are implemented having three frame stores since three stores is the minimum number of stores to perform conventional decode processes. Since a conventional video decoder system displays the B frame store as the B frame is decoded, extensive graphics manipulation is difficult and/or expensive to implement via a conventional video decoder system.
It would be desirable to have an video image display that (i) provides additional graphics manipulation after the picture has been decoded and (ii) does not limit the features that can be added.